A phased array device outputs radio waves different in phase from each other from a plurality of antennas adjacent to each other, and thereby transmits the radio waves in one direction. Such phased array devices are expected to be applied to vehicle-mounted radars and apparatuses for a fifth generation mobile communication system in the future.
A phased array device uses phase shift circuits that adjust the phases of radio waves output from a plurality of antennas. In order to shift the phase of an input signal (phase shift) by a specified amount of phase shift, a phase shift circuit adjusts the amplitudes of two signals different in phase from each other by 90 degrees in respective variable amplifier circuits according to the amount of phase shift, and synthesizes the two signals adjusted in amplitude. A signal having a phase corresponding to a ratio between the amplitudes is thereby output.
However, the existing phase shift circuit may cause phase deviation before synthesizing the two signals in cases of small degrees of amplification (amplification factor) in the variable amplifier circuits. Therefore, the phase shift by the desired amount of phase shift may not be performed, so that an error may occur in output phase.
The followings are reference documents.    [Document 1] Japanese Laid-open Patent Publication No. 2003-133906,    [Document 2] Japanese Laid-open Patent Publication No. 2011-10192, and    [Document 3] Japanese Laid-open Patent Publication No. 2003-229738